Involuntary secondhand smoke (SHS) exposure in homes is an entirely preventable public health threat that disproportionately burdens young children in communities of low socioeconomic position. Our NCI-funded Community Networks Program MassCONECT previously demonstrated the efficacy of motivational intervention (Ml) to protect vulnerable children from SHS. We now propose a community-based participatory research (CBPR) initiative to evaluate the effectiveness of Ml compared with usual best practices (UBP) by having parents voluntarily adopt smoke-free home policies to protect children from SHS. Ml will be developed in conjunction with community partners, integrated into a health department-sponsored home visiting program for high-risk children, and delivered by trained community health workers. Aim 1): Develop and integrate an intervention to promote smoke-free homes into existing Early Intervention (El) home visiting programs for high-risk children (ages 0-3 years) in three Massachusetts cities: Boston, Worcester, and Lawrence. El programs, sponsored by the Massachusetts Department of Public Health, facilitate family interactions with children to meet appropriate developmental milestones. For eligible El households, ie where either the parent/primary caregiver (or the spouse/significant other) smokes and no smoke-free home policy exists, UBP consists of written materials about SHS and smoke-free homes, quitlines and other publicly available cessation services. Ml will be delivered by a trained community health worker, using specifically developed messages culturally and linguistically tailored to the client. Aim 2: Assess the effectiveness of UBP vs. Ml to reduce SHS exposure for at-risk children: We will enroll 500 eligible El households in the three cities and randomize them to UBP or Ml. We hypothesize that compared to UBP, Ml will result in the primary outcomes of: i) significantly higher rates of adoption of a smoke-free household policy, ii) significantly lower numbers of cigarettes smoked inside the home, iii) significantly lower domestic SHS, and iv) significantly lower child SHS exposure. This intervention, a product of a strong academic-community-health department collaboration, rigorously applies CBPR principles, builds capacity for communities, maximizes the potential for sustainability through partnership with existing state-funded resources, and offers an innovative venue to protect vulnerable children and reduce disparities. This study encourages the adoption of smoke-free home policies to protect at-risk children from involuntary exposure to secondhand smoke. By integrating such community efforts into home visiting programs sponsored by health departments, the study offers an innovative strategy to promote the health of kids.